Microbicidal composition

ABSTRACT

A microbicidal composition containing: (a) 2-methyl-4-isothiazolin-3-one; and (b) 2,2-dibromo-3-nitrilopropionamide.

This invention relates to a combination of selected microbicides havinggreater activity than would be observed for the individual microbicides.

In some cases, commercial microbicides cannot provide effective controlof microorganisms, even at high use concentrations, due to weak activityagainst certain types of microorganisms, e.g., those resistant to somemicrobicides. Combinations of different microbicides are sometimes usedto provide overall control of microorganisms in a particular end useenvironment. For example, a combination of: (i) a 3:1 mixture of5-chloro-2-methylisothiazolin-3-one and 2-methylisothiazolin-3-one; and(ii) 2,2-dibromo-3-nitrilopropionamide is disclosed in U.S. Pat. No.3,929,562. However, there is a need for additional combinations ofmicrobicides having enhanced activity against various strains ofmicroorganisms to provide effective control of the microorganisms thatis both quick and long lasting. Moreover, there is a need forcombinations containing low levels of halogenated isothiazolones. Theproblem addressed by this invention is to provide such additionalcombinations of microbicides.

STATEMENT OF THE INVENTION

The present invention is directed to a microbicidal compositioncomprising: (a) 2-methyl-4-isothiazolin-3-one; and (b)2,2-dibromo-3-nitrilopropionamide; wherein said composition contains nomore than 12% halogenated 4-isothiazolone-3-ones.

DETAILED DESCRIPTION OF THE INVENTION

“MI” is 2-methyl-4-isothiazolin-3-one, also referred to by the name2-methyl-3-isothiazolone. “DBNPA” is 2,2-dibromo-3-nitrilopropionamide.

As used herein, the following terms have the designated definitions,unless the context clearly indicates otherwise. The term “microbicide”refers to a compound capable of inhibiting the growth of or controllingthe growth of microorganisms at a locus; microbicides includebactericides, fungicides and algaecides. The term “microorganism”includes, for example, fungi (such as yeast and mold), bacteria andalgae. The term “locus” refers to an industrial system or productsubject to contamination by microorganisms. The following abbreviationsare used throughout the specification: ppm=parts per million by weight(weight/weight), mL=milliliter, ATCC=American Type Culture Collection,and MIC=minimum inhibitory concentration. Unless otherwise specified,temperatures are in degrees centigrade (° C.), and references topercentages (%) are by weight. “Salt-free” means that the compositioncontains zero or up to 0.5%, preferably zero or up to 0.1%, and morepreferably zero or up to 0.01%, of metal salt, based on weight of thecomposition.

The compositions of the present invention unexpectedly have been foundto provide enhanced microbicidal efficacy at a combined activeingredient level lower than that of the individual microbicides. Themicrobicidal compositions of the present invention contain relativelylow levels of halogenated 3-isothiazolones, preferably no more than 5%,more preferably no more than 2%, more preferably no more than 1.2%, morepreferably no more than 0.5%, and most preferably no more than 0.1%.Percentages of halogenated 3-isothiazolones in the composition of thisinvention are based on the total weight of active ingredients in thecomposition, i.e., the microbicides exclusive of any amounts ofsolvents, carriers, dispersants, stabilizers or other materials whichmay be present. Microbicidal compositions dependent on the presence ofhalogenated 3-isothiazolone are susceptible to chemical degradation andmay require additional stabilizer components, such as the aforementionedmetal salt stabilizers; salt stabilizers sometimes create unacceptableproperties in finished formulations. For this reason it is desirable toprovide microbicide formulations substantially free of halogenated3-isothiazolone, but that still provide the degree of antimicrobialprotection provided by the halogenated 3-isothiazolones; such are themicrobicidal compositions of the present invention that are based on2-methyl-3-isothiazolone, which do not require metal stabilizers.

Preferably, a weight ratio of 2-methyl-4-isothiazolin-3-one to2,2-dibromo-3-nitrilopropionamide is from 150:1 to 1:10, more preferablyfrom 100:1 to 1:7, more preferably from 10:1 to 1:1 and most preferablyfrom 6:1 to 1:1.

The microbicides in the composition of this invention may be used “asis” or may first be formulated with a solvent or a solid carrier.Suitable solvents include, for example, water; glycols, such as ethyleneglycol, propylene glycol, diethylene glycol, dipropylene glycol,polyethylene glycol, and polypropylene glycol; glycol ethers; alcohols,such as methanol, ethanol, propanol, phenethyl alcohol andphenoxypropanol; ketones, such as acetone and methyl ethyl ketone;esters, such as ethyl acetate, butyl acetate, triacetyl citrate, andglycerol triacetate; carbonates, such as propylene carbonate anddimethyl carbonate; and mixtures thereof. It is preferred that thesolvent is selected from water, glycols, glycol ethers, esters andmixtures thereof. Suitable solid carriers include, for example,cyclodextrin, silicas, diatomaceous earth, waxes, cellulosic materials,alkali and alkaline earth (e.g., sodium, magnesium, potassium) metalsalts (e.g., chloride, nitrate, bromide, sulfate) and charcoal.

When a microbicide component is formulated in a solvent, the formulationmay optionally contain surfactants. When such formulations containsurfactants, they are generally in the form of emulsive concentrates,emulsions, microemulsive concentrates, or microemulsions. Emulsiveconcentrates form emulsions upon the addition of a sufficient amount ofwater. Microemulsive concentrates form microemulsions upon the additionof a sufficient amount of water. Such emulsive and microemulsiveconcentrates are generally well known in the art; it is preferred thatsuch formulations are free of surfactants. U.S. Pat. No. 5,444,078 maybe consulted for further general and specific details on the preparationof various microemulsions and microemulsive concentrates.

A microbicide component also can be formulated in the form of adispersion. The solvent component of the dispersion can be an organicsolvent or water, preferably water. Such dispersions can containadjuvants, for example, co-solvents, thickeners, anti-freeze agents,dispersants, fillers, pigments, surfactants, biodispersants,sulfosuccinates, terpenes, furanones, polycations, stabilizers, scaleinhibitors and anti-corrosion additives.

The microbicides may be formulated separately or together. When bothmicrobicides are each first formulated with a solvent, the solvent usedfor the first microbicide may be the same as or different from thesolvent used to formulate the other commercial microbicide. It ispreferred that the two solvents are miscible. In the alternative, thefirst microbicide and the other microbicide may be combined directly andthen a solvent added to the mixture.

Those skilled in the art will recognize that the microbicide componentsof the present invention may be added to a locus sequentially,simultaneously, or may be combined before being added to the locus. Itis preferred that the first microbicide and the second microbicidecomponent be added to a locus simultaneously or combined prior to beingadded to the locus. When the microbicides are combined prior to beingadded to a locus, such combination may optionally contain adjuvants,such as, for example, solvent, thickeners, anti-freeze agents,colorants, sequestrants (such as ethylenediamine-tetraacetic acid,ethylenediaminedisuccinic acid, iminodisuccinic acid and salts thereof),dispersants, surfactants, biodispersants, sulfosuccinates, terpenes,furanones, polycations, stabilizers, scale inhibitors and anti-corrosionadditives.

The microbicidal compositions of the present invention can be used toinhibit the growth of microorganisms by introducing a microbicidallyeffective amount of the compositions onto, into, or at a locus subjectto microbial attack. Suitable loci include, for example: cooling towers;air washers; mineral slurries; wastewater treatment; ornamentalfountains; reverse osmosis filtration; ultrafiltration; ballast water;evaporative condensers; heat exchangers; pulp and paper processingfluids; plastics; emulsions; dispersions; paints; latices; coatings,such as varnishes; construction products, such as mastics, caulks, andsealants; construction adhesives, such as ceramic adhesives, carpetbacking adhesives, and laminating adhesives; industrial or consumeradhesives; photographic chemicals; printing fluids; household products,such as bathroom and kitchen cleaners; cosmetics; toiletries; shampoos;soaps; detergents; industrial cleaners; floor polishes; laundry rinsewater; metalworking fluids; conveyor lubricants; hydraulic fluids;leather and leather products; textiles; textile products; wood and woodproducts, such as plywood, chipboard, flakeboard, laminated beams,oriented strandboard, hardboard, and particleboard; petroleum processingfluids; fuel; oilfield fluids, such as injection water, fracture fluids,and drilling muds; agriculture adjuvant preservation; surfactantpreservation; medical devices; diagnostic reagent preservation; foodpreservation, such as plastic or paper food wrap; pools; and spas.

Preferably, the microbicidal compositions of the present invention areused to inhibit the growth of microorganisms at a locus selected fromone or more of emulsions, dispersions, paints, latices, householdproducts, cosmetics, toiletries, shampoos, soaps, detergents, machiningfluids and industrial cleaners. In particular, the microbicidalcompositions are useful in emulsions, dispersions, paints and latices.

When the synergistic compositions of the present invention are used inpersonal care compositions, the formulated compositions may alsocomprise one or more ingredients selected from UV radiation-absorbingagents, surfactants, rheology modifiers or thickeners, fragrances,moisturizers, humectants, emollients, conditioning agents, emulsifiers,antistatic aids, pigments, dyes, tints, colorants, antioxidants,reducing agents and oxidizing agents.

The specific amount of the composition of this invention necessary toinhibit or control the growth of microorganisms in a locus depends uponthe particular locus to be protected. Typically, the amount of thecomposition of the present invention to control the growth ofmicroorganisms in a locus is sufficient if it provides from 0.1 to10,000 ppm active ingredient of the composition in the locus. It ispreferred that the active ingredients of the composition be present inthe locus in an amount of at least 0.5 ppm, more preferably at least 1ppm, more preferably at least 10 ppm and most preferably at least 50ppm. It is preferred that the active ingredients of the composition bepresent in the locus in an amount of no more than 5000 ppm, morepreferably no more than 3000 ppm, more preferably no more than 1000 ppm,and most preferably no more than 500 ppm.

EXAMPLES

The synergism of the combination of the present invention wasdemonstrated by testing a wide range of concentrations and ratios of thecompounds.

One measure of synergism is the industrially accepted method describedby Kull, F. C.; Eisman, P. C.; Sylwestrowicz, H. D. and Mayer, R. L., inApplied Microbiology 9:538-541 (1961), using the ratio determined by theformula:Q _(a) /Q _(A) +Q _(b) /Q _(B)=Synergy Index (“SI”)wherein:

-   -   Q_(A)=concentration of compound A (first component) in ppm,        acting alone, which produced an end point (MIC of Compound A).    -   Q_(a)=concentration of compound A in ppm, in the mixture, which        produced an end point.    -   Q_(B)=concentration of compound B (second component) in ppm,        acting alone, which produced an end point (MIC of Compound B).    -   Q_(b)=concentration of compound B in ppm, in the mixture, which        produced an end point.

When the sum of Q_(a)/Q_(A) and Q_(b)/Q_(B) is greater than one,antagonism is indicated. When the sum is equal to one, additivity isindicated, and when less than one, synergism is demonstrated. The lowerthe SI, the greater the synergy shown by that particular mixture. Theminimum inhibitory concentration (MIC) of a microbicide is the lowestconcentration tested under a specific set of conditions that preventsthe growth of added microorganisms.

Synergy tests were conducted using standard microtiter plate assays withmedia designed for optimal growth of the test microorganism.Full-strength nutrient medium (Trypticase Soy Broth, TSB) or mineralsalts-glucose medium (M9G) with added yeast extract was used for testingbacteria. High resolution MICs were determined by adding varying amountsof microbicide to one column of a microtitre plate and doing subsequentten-fold dilutions using an automated liquid handling system to obtain aseries of endpoints ranging from 2 ppm to 10,000 ppm active ingredient.The combinations of the present invention were tested against threebacteria, Pseudomonas aeruginosa (P. aeruginosa - - - ATCC #15442),Enterobacter aerogenes (ATCC #13048), and Kiebsiella pneumoniae (ATCC#13883). The bacteria were used at a concentration of about 10⁸ bacteriaper mL. These microorganisms are representative of natural contaminantsin many consumer and industrial applications. The plates were visuallyevaluated for microbial growth (turbidity) to determine the MIC aftervarious incubation times at 30° C.

To evaluate “Speed of Kill” an aliquot of 30 g of pH 8 TSB was dispensedin sterile 2 oz (60 mL) jars. Biocides stock solution was added intoeach jar to achieve the final concentration. The test samples wereinoculated with 0.3 ml of mixed bacterial inoculum (resulting in 10⁶/mlbacteria per ml of test solution). Samples were then placed in a shakerwater bath at 30° C. Bacterial growth was monitored via the microtiterMPN method using the BECKMAN AUTOMATIC 2000 Workstation after 30 min, 1,4, 24, 48, 72 hours and again 6-7 days contact time. The microtiterplates were incubated at 30° C. for 2 days.

The test results for demonstration of synergy of the microbicidecombinations of the present invention are shown below in the Tables. Ineach test, First Component (A) was MI and the Second Component (B) wasDBNPA. “NG” means that no growth was observed. Each table shows thespecific combinations of MI and the second component; results againstthe microorganisms tested with incubation times; the end-point activityin ppm measured by the MIC for MI alone (Q_(A)), for the secondcomponent alone (Q_(B)), for MI in the mixture (Q_(a)) and for secondcomponent in the mixture (Q_(b)); the calculated SI value; and the rangeof synergistic ratios for each combination tested (MI/second componentor A/B). TABLE I MI Alone and in Combination with DBNPA vs Bacteria inTSB Medium CFU/ml Bacteria Log Reduction vs Control after PPM AI Added @30° C. for: MI DBNPA 30 min 1 hr 4 hr 24 hr 48 hr 72 hr 168 0 0 25 0−0.3 0.0 0.2 −1.3 −2.0 — — 1 −1.1 0.2 0.0 −1.4 — — — 2 0.6 −0.3 −0.3−0.8 — — — 5 −0.1 0.0 0.0 −1.2 −2.3 — — 9 0.4 0.4 0.4 0.7 −2.0 — — 230.8 −0.4 0.2 4.6 >5.4 3.2 −2.6 50 0 0.4 0.2 0.4 −0.6 −1.6 — — 1 0.4 0.00.4 0.0 −2.0 — — 2 0.2 0.0 0.0 0.4 −1.0 — — 5 0.4 0.6 0.0 0.7 −2.0 — — 90.4 0.2 0.0 1.1 −1.0 — — 23 0.6 0.4 0.4 >5.4 >5.4 5.0 −2.6 75 0 0.2 0.2−0.3 0.2 −2.0 — — 1 −0.1 0.0 −0.3 1.2 −1.6 — — 2 0.6 0.2 0.4 0.8 −2.3 —— 5 0.2 −0.3 0.0 1.2 0.0 −2.3 — 9 0.6 0.7 0.2 1.0 0.0 −0.8 — 23 0.6 1.00.4 >5.4 4.0 4.9 0.4 100 0 0.4 0.6 0.2 0.8 1.7 0.0 −2.8 1 0.6 0.2 0.20.8 1.4 0.0 −2.8 2 0.2 0.4 0.2 1.0 1.6 0.2 −2.8 5 −0.1 0.0 0.4 2.0 2.21.2 −2.8 9 0.6 0.2 0.7 2.0 1.7 1.0 −2.6 23 −0.1 0.2 0.7 >5.4 >5.4 >5.41.7 150 0 0.6 0.2 0.0 −0.2 1.7 0.4 −2.0 1 0.2 0.0 0.7 1.4 2.0 1.0 −2.0 20.4 −0.3 1.2 1.0 1.6 1.4 −2.2 5 0.6 0.0 0.7 1.6 2.0 2.2 −2.2 9 0.2 0.40.7 1.0 2.4 2.7 −2.6 23 0.6 0.2 1.2 >5.4 >5.4 >5.4 1.2 0 1 0.6 −0.6 −1.0−2.6 — — — 2 −0.1 −0.3 −0.8 −1.4 — — — 5 0.4 −0.3 −0.8 −1.6 — — — 9 0.40.0 −1.0 −2.0 — — — 23 0.4 0.2 −1.0 −1.4 — — —

Log reduction was calculated based on bacterial reduction vs. 0 timeuntreated sample.

Detection limit=1.1 log bacterial growth

Negative (−) log reduction values indicate growth. TABLE II Synergy ofMI in Combination with DBNPA vs Mixed Bacteria in TSB in Speed of KillTest (5-log reduction criteria used for synergy) Minimum EffectiveEffective Concentration Concentration (ppm AI) (ppm AI) ALONE* INCOMBINATION Time MI DBNPA MI DBNPA S.I. 24 hr 300 46 50.0 23 0.67 48 hr300 46 25.0 23 0.58 72 hr 300 46 50.0 23 0.67*Minimum effective concentrations alone were determined by the method ofLazonby (when no end point value was measured, i.e., the highest levelalone failed, the value reported in the table to represent a minimumeffective level was 2× the highest level tested), see, e.g., U.S. Pat.No. 5,980,758.

TABLE III Synergy Results of MI and DBNPA using the Minimum InhibitoryConcentration (MIC) Tests versus Mixed Bacteria MIC Values (ppm AI) MICValues (ppm AI) ALONE IN COMBINATION Test Media DBNPA MI DBNPA MI S.I.1/10 TSB 45 38 8.1 19 0.68 M9G + 0.1% 45 38 8.1 10 0.44 yeast extractM9G + 0.1% 45 38 16.2 2.5 0.43 yeast extractMIC values determined after 24 hours at 30° C.

1. A microbicidal composition comprising: (a)2-methyl-4-isothiazolin-3-one; and (b)2,2-dibromo-3-nitrilopropionamide; wherein said composition contains nomore than 12% halogenated 4-isothiazolone-3-ones.
 2. The composition ofclaim 1 in which a weight ratio of 2-methyl-4-isothiazolin-3-one to2,2-dibromo-3-nitrilopropionamide is from 150:1 to 1:10.
 3. Thecomposition of claim 2 in which the composition contains no more than 2%halogenated 4-isothiazolone-3-ones.
 4. The composition of claim 3 inwhich the weight ratio of 2-methyl-4-isothiazolin-3-one to2,2-dibromo-3-nitrilopropionamide is from 100:1 to 1:7.
 5. Thecomposition of claim 4 in which the composition contains no more than1.2% halogenated 4-isothiazolone-3-ones.
 6. The composition of claim 5in which the weight ratio of 2-methyl-4-isothiazolin-3-one to2,2-dibromo-3-nitrilopropionamide is from 10:1 to 1:1.
 7. Thecomposition of claim 6 in which the composition contains no more than0.5% halogenated 4-isothiazolone-3-ones.